CTNI-17. A PHASE 2 STUDY OF SAFETY AND EFFICACY OF CONCURRENT ACT001 AND RADIATION TREATMENT FOLLOWED BY ACT001 MAINTENANCE THERAPY IN NEWLY DIAGNOSED PEDIATRIC PATIENTS WITH DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)

Abstract

Abstract BACKGROUND ACT001, an oral parthenolide derivative targeting NF-κB and STAT3 pathways, has shown activity in preclinical DIPG model and dose-finding study in patients with diffuse midline glioma. We further evaluated safety and activity of ACT001 in newly diagnosed DIPG patients and presented the interim data from exploratory stage of this phase 2 study. METHODS Eligible patients ≥ 5 and ≤ 15 years old were treated with concurrent ACT001 and standard radiation followed by ACT001 single agent treatment in this single arm, open label, multicenter phase 2 study. Tumor lesions were evaluated at baseline, 4 weeks and then every 8 weeks after the end of radiation therapy per RAPNO criteria with ORR as primary endpoint. Interim data analysis was performed when data from approximately 20 efficacy evaluable patients became available during the exploratory stage of this study. RESULTS Among 30 patients enrolled since Sept, 2023, 27 took at least one dose of ACT001 by April 30th, 2024, the data cutoff date (with exception for May 15th as the MRI cutoff date). While 3 patients were quickly taken off study due to a disease progression or consent withdrawal, 17 out of 27 patients finished at least one post-radiation MRI exam whereas MRI results are pending for 7 other patients by this interim analysis. Median age was 8 years old and male to female patient ratio is 17:10. The median LPS score is 70.0. Among 17 efficacy evaluable subjects, 8 patients exhibited partial response (6 confirmed) including one with a deep tumor reduction (-91.7%) noted three months after end of radiation. Among 9 other evaluable patients, 5 and 4 exhibited ongoing stable disease and progressive disease respectively. Subject 05001 was considered PD despite confirmed objective response for the target lesion upon development of new lesions. Two patients withdrew consent after finishing first post-radiation MRI scans despite initial tumor burden reduction which were both close to PR criteria. Patients tolerated concurrent ACT001 and radiation well. In total, 289 TEAE and 184 TRAE events were reported in 23 and 22 patients respectively. There were two ACT001-related grade 3 or 4 adverse events including one grade 4 hemorrhagic tumor necrosis (a SUSAR event and the only ACT001 related SAE) likely due to a therapeutic effect of ACT001 and one clinically insignificant grade 3 decreased lymphocyte count. Most common TRAE were manageable grade 1 or 2 events such as weight loss (15/184), vomiting (71/184), decreased lymphocyte count (13/184) and abdominal bloating (7/184). No study discontinuation occurred due to ACT001 or radiation related TRAEs. Conclusion. Concurrent ACT001 and radiation treatment was well tolerated. Preliminary evidence of anti-tumor activity was shown in about 50% efficacy evaluable DIPG patients. It is worthwhile to explore ACT001 and temozolomide combination in future study based on safety and efficacy signal from DIPG and recurrent GBM studies. The confirmatory stage of this study is in planning to further evaluate the anti-tumor efficacy signal of this NF-κB and STAT3 dual inhibitor.